A Resected Case of Hepatic Angiomyolipoma with Tumor Hemorrhage and Undetectable Fat Causing Diagnostic Difficulty

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INTRODUCTION: Hepatic angiomyolipoma (AML) is a rare, benign mesenchymal tumor with variable imaging features, often complicating differentiation from malignancy. We report a case of hepatic AML that showed progressive enlargement due to intratumoral hemorrhage, without detectable fat on imaging.

CASE PRESENTATION: A woman in her 70s with no history of chronic liver disease had previously undergone surgery for lung adenocarcinoma and for localized nodular hyperplasia of the liver. Routine follow-up imaging revealed an enlarging liver mass in the right hepatic lobe, leading to her referral for further evaluation. Tumor markers were within normal ranges, and liver function remained intact. Non-contrast CT showed a low-attenuation nodule, and contrast-enhanced CT demonstrated ring-like peripheral enhancement with a hypovascular center. Magnetic resonance imaging showed low signal on T1-weighted images and high signal on T2-weighted images, with no signal loss in opposed-phase imaging. Ultrasonography demonstrated a low echogenicity within the tumor and high echogenicity in the surrounding area, with no clear contrast effect. The preoperative diagnosis suggested either a hematoma or a necrotic nodule. Given the progressive growth and inconclusive imaging, malignancy could not be excluded. A laparoscopic hepatectomy was performed for definitive diagnosis. The resected tumor was a 2.3 × 2.0 × 1.4 cm well-demarcated, light brown mass with areas of hemorrhage and cystic change. Histopathology confirmed hepatic AML with tumor hemorrhage and extramedullary hematopoiesis.

CONCLUSIONS: Hepatic AML may exhibit progressive growth despite lacking typical imaging features such as intratumoral fat or vascularity, making preoperative diagnosis difficult. In cases where malignancy cannot be ruled out, surgical resection should be considered after careful evaluation of both benign and malignant possibilities.